Internal-combustion engine



April 21, 1925.

M. PRETOT I INTERNAL COMBUSTION ENGINE Original Filed March 25, 1920 1 carb I/z v-eafar W Patented Apr. 21, 19 25.

umrep STATES MARCEL BRETOT, OF ENSISHEIM, HAUT-RHIN, FRANCE.

INTERNAL-COMBUSTION ENGINE.

Application filed March 25, 1920, Serial No. 368,626. Renewed March 18, 1925.

(GRANTED UNDER THE PROVISIONS F THE ACT OF MARCH 3, 1921, 41 STATQL, 1313.)

To all whom it may concern i Be it known that I, MAnonL Pniiro'r, a citizen of the Republic of France, and residing at 7 Faubourg de Belfort, Ensisheim, Haut- Rhin. France, have invented certain new and useful Improvements in Internal-Combustion Engines (for which I have received a patent in France, No. 502,742, February 27, 1920), of which the following is a specifica- 10 tion.

This invention relates to two-cycle internal combustion engines, the general arrangement and operation of which are well known. It is usual in such engines to admit fuel mix- 16 turc to the cylinder while the exhaust port is open, so that the entering mixture may displace the gases burned during the previous power stroke. The exhaust port is then closed, and attempts have been made to 20 close it at such a time that all of the burned gases are expelled but none of the fresh fuel mixture has escaped. This, however, is dif- Vficult if not possible to accomplish, and it has been found that the engines possess either one of the following disadvantages:

1) either some of the fresh mixture escapes through the open exhaust port, resulting in unnecessary loss of fuel, or (2) some of the burned. gases are retained in the cylinder,

diluting the mixture and preventing the obtaining of the maximum power.

The principal objects of this invention are to provide a two-cycle engine free from the above disadvantages, that is, to provide means for expelling all of the burned gases and yet prevent the loss of any fuel mixture.

Other objects will be apparent from the annexed description and from the accompanying drawings, in which:

Figure 1 is a vertical section of an engine constructed according to one form of my invention, the means for operating the valves being indicated diagrammatically, and

Figure 2 is a sectional view of a portion of a modified form of engine.

Referrin to Figure 1, the engine comprises a cy inder A terminating in a gastight crank case F and provided with a piston B, which reciprocates in the cylinder and crank case in the well known manner. A

pitman C journaled in the piston drives theeccentric D of the crank shaft. In one end of the cylinder is an exhaust valve of the poppet type K which is normally held closed ture in the crank case.

by a spring Z, and ner the other end of the cylinder is a scaven ing port L, supplied with air under pressure from any suitable pump or blower S which maybe conveniently driven from the crank shaft through a belt or other driving means P. A port.() is provided in the crank case wall in a position to be covered and uncovered by the piston B and is connected to a. carburetor or other suitable source of fuel supply, not shown. A conduit or duct M affords communication between the lower portion of the crank case and the lower portion of the cylinder and is normally closed by a poppet valve M which is normally seated by a spring m. A train of gears 1, 2, 3, and t is driven by the crank shaft and operates a pair of cams Q and R, the cam Q operating the push rod Q to unseat the valve M. and the cam R operating the push rod R to unseat the valve K.

The engine operates as follows: Assume that the piston is at the upper end of its stroke and that the crank case is full of combustible mixture at atmospheric pressure, the valves K andM are closed and the port Iris covered by the piston. The cylin der above the piston is filled with combusti ble mixture under pressure and this'is fired by any suitable ignition means. not shown. As the pisto n'begins to travel downward it covers the port 0 and compresses the Near the end of the stroke the cam R opens the exhaust valve K permitting the burned gases to escape, and substantially at the end of the stroke the piston uncovers the port L. Air from the blower S is forced through the cylinder and drives out any burned-gases remaining. The piston now passes dead center and covers the port L and the exhaust valve K is closed. At this moment, the admission valve M is opened by the cam Q, and push rod Q, and fuel mixture under pressure'in the crank case flows into the cylinder, filling the latter with combustible mixture. As the piston travels upward the valve M is closed and the mixture in the cylinder A is compressed. At the same time the piston produces a reduction of pressure in the crank case F, and when it has reached the upper end of its stroke, the port 0 is uncovered and a new charge of fuel mixture flows into the crank case. This cycle then repeats itself.

' cylinder.

'-and It ehould be noted that the blast of scavenging air flows through the cylinder at the eliminatend of each stroke thus com letel ing any burned gases and fil ingtiie cylinder with fresh air. At the same time the admission valve M is closed so that no fuel mixture is lost, both the scavenging port and the exhaust valve being closed before the admission valve is opened to supply fuel to the A modified construction is shown in Figure 2, wherein the port L is connected to the carburetor or other source of fuelsupply and the port 0 is open tothe atmosphere, the mechanically driven blower being eliminated. In this construction, the upward movement of the piston draws air into the crank case, and the downward movement com resses it for scavenging. The valves K are so timed that M is open while K is open and as the piston reaches the end of its stroke, a blast of scavenging air from the crank cases passes through the cylinder. The valve M is closed, however, before the piston uncoyers the port Lso that no fuel 1s lost is clailnedas new and desired to be secured by Letters Patent is: 7

1'. twocycle internal combustion engine comprising'in combination, acylinder, a gastight crank case, and a iston ,reciprocable therein, means for supp ying fuel mixture to the crank case, means or conducting fuel mixture from the crank case tothe cyllnder,

means for blowing scavenging air through the cylinder, and means for preventing admission of fuel from the crank case to the cylinder while scavenging.

2. A two-cycle lnternal combustion engine comprising in combmatmn, a cylinder, a gas tight crank case, and a piston reciprocable therein, a sca enging port near one end of the cylinder adapted to be opened by the piston near the end of its power stroke, a normally closed exhaust valveat the other end of the cylinder, a conduit afiordin communication between the crank case an cylinder, a normally closed admission valve in said conduit, means for opening the admission valve, means for opening the exhaust valve while the scavenging port is uncovered, and means'for supplying air under pressure to the scavenging port, the admission valve opening means being adapted to operate only when both the scavenging port and the exhaust valve are closed- In testimony whereof I- afiixmy signature in presence of a witness. MARCEL PRETOT.

Witness:

PAUL COULOMB. 

